A 0.5 kg ball is about to roll off the edge of a 1.5 m tall table. What is its current potential energy? (g = 9.8 ms²) ?
- NCSLv 71 month ago
Depends on your frame of reference. If you consider the ground to be the point of 0 gravitational potential energy, then at the tabletop
GPE = 0.5kg * 9.8m/s² * 1.5m = 7.4 J
But if the tabletop is your 0 GPE height, then at the tabletop
GPE = 0 J
And if the ceiling 2 m above the table is your 0 GPE reference, then at the tabletop
GPE = 0.5kg * 9.8m/s² * -2m = -9.8 J
The 0 GPE height can be set anywhere; it's the CHANGES in height that matter.
Hope this helps!
- Wayne DeguManLv 71 month ago
PE = mgh
so, 0.5 x 9.8 x 1.5 => 7.35 Joules